1. Field of the Invention
The present invention relates to an image processing apparatus, particularly, an imaging processing apparatus characterized by processing in data transfer between memories.
2. Description of the Related Art
Computer graphics is frequently utilized in various CAD (Computer Aided Design) systems, amusement equipments, or others. Particularly, along with the progress in image processing technology in recent years, systems using three-dimensional computer graphics are rapidly and widely spread.
Three-dimensional computer graphics involves frequent access to storage circuits like DRAM in order to perform real-time processing of a large amount of image data. For this purpose, rendering circuits and DRAMs are built in a semiconductor chip. A rendering circuit, for example, includes an alpha blend circuit in addition to a texture circuit to carry out texture processing. When writing image data to a DRAM, for each pixel data, the alpha blend circuit mixes the data to be written (source data) and the data read from a destination address for writing (destination data), based upon an alpha data selected from either the source data or the destination data, and carries out alpha blending to write the mixed data to the above address.
Further, a rendering circuit carries out bit block transfer (bitblt) that includes local transfer, namely, data transfer within the DRAM, and host-local transfer, namely, data transfer from an external memory outside the semiconductor chip to the DRAM.
In a rendering circuit of the related art, the path for data transfer in the above bitblt is configured to be independent from the alpha blend circuit.
Recently, the demand for image processing at a higher speed has increased, and it is required to perform alpha blending or other image processing during data transfer in bitblt.
However, a rendering circuit of the related art cannot meet this requirement, because in a rendering circuit of the related art, as shown above, the path for data transfer in bitblt is configured independently from the alpha blend circuit.